The present invention relates to a packaging structure of an integrated circuit device having a photo detecting part, such as an amplifier-embedded light receiving device for an optical disk unit.
FIG. 7 is a block diagram of an optical disk unit having a laser unit (LDU) shown in terms of functions. Referring to FIG. 7, the laser unit includes a laser device 52 and an integrated circuit device 53 having a photo detecting part (optoelectronic integrated circuit (OEIC)). Laser light is emitted from the laser device 52 toward an optical disk 51, and reflected light from the optical disk 51 is received by the photo detecting part of the integrated circuit device 53.
For improvement of the recording density of an optical disk, the beam diameter of laser light for irradiation of the optical disk has been narrowed. For attaining a narrower beam diameter, the wavelength of laser light has been gradually made shorter. For example, while the laser wavelength was 780 nm for CDs, it is 650 nm for DVDs. For next-generation DVDs, a further short laser wavelength is used for higher density.
The inventors of the present invention set out prototype fabrication and experiments using short-wavelength blue laser, and in this relation, the following problem was found. That is, a transparent resin was used for encapsulation of a device, as used for conventional OEICs for DVDs. In this case, however, the transparent resin was partly deformed/degraded when it was irradiated with short-wavelength blue laser light.
The above problem did not occur in the conventional OEICs for DVDs. The cause for this problem has not yet been clarified, but presumed pertinent to this problem as one factor is that with the shortened wavelength of the laser light, the energy of the laser light increases from the conventional level, causing generation of heat from the light absorbed into the resin.